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from the issue of February 12, 2004
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Fans keep Hamilton Hall safe, efficient
BY KIRK CONGER, UNL FACILITIES (BUILDING SYSTEMS MAINTENANCE)
The new exhaust fans on top of Hamilton Hall make a little more noise than the old ones, and they stick up a little farther. Their biggest impact, however, is to provide healthier work conditions while reducing the cost of heating and cooling the building.
| | Engineers with Facilities Management and Planning created these controls for exhaust hoods in Hamilton Hall to help make the building more energy efficient while removing air from the building’s chemistry labs.
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The fans contain two features that contribute to the savings: New ventilation controllers reduce the amount of air leaving through exhaust vents, and an energy recovery system cuts the cost of conditioning fresh air entering the building.
In many UNL buildings, most of the air brought in by large air handlers is eventually returned to the air handler, reconditioned and reused. The amount of fresh air pulled into the building is limited to about 30 percent of the total flow, which is enough to keep the building fresh and occupants healthy.
Hamilton Hall is different. It has one of the largest air handlers on campus, and it uses 100 percent fresh air. Because the building contains many chemistry laboratories, all of the building’s air is exhausted and replaced with fresh outdoor air every 15-20 minutes. It’s expensive but necessary because it isn’t safe to recirculate contaminated air from the labs. Therefore, saving energy in this situation requires two steps: minimizing the amount of air exhausted from the building, and capturing as much energy as possible from the air before releasing it.
Like many of UNL’s newer buildings, dampers in each room in Hamilton Hall bring in only enough air to satisfy the thermostat’s setting. But unlike other buildings, Hamilton also has many exhaust fume hoods, which are special cabinets used for chemical experiments from which air is exhausted.
To cope with this complexity, engineers in Facilities Management and Planning developed a fume-hood control that keeps air flowing out through exhaust vents and fume hoods but still allows in only the air needed to keep the room comfortable and the exhaust hoods working. The fume hood controllers are based on UNL’s electronic thermostats. But unlike the thermostats, which react to temperature changes in a minute or two, the fume hood controllers respond to pressure differences in a fraction of a second. By minimizing the exhaust air, the controllers also reduce the electricity used by supply and exhaust fans.
That exhaust air, however, still contains a lot of expensive energy. The Nebraska Utilities Corporation added $350,000 to the building renovation budget to install heat recovery coils in the exhaust and intake air streams.
These coils, which look like large automobile radiators, capture heat from the exhaust air and transfer it to the incoming air. On a cold winter day, this warms the incoming air by about 20 degrees. Then heating coils warm the air to its normal supply temperature. Pumps circulate an antifreeze solution between the exhaust coils at roof level and the air handlers in the basement to transfer the recovered heat.
The heat recovery system has been operating since December and is on track to save about $60,000 per year. More savings are expected from optimizing controls.
UNL Facilities Management & Planning has a number of other projects under way to reduce energy costs on campus. For more information or to make a suggestion, e-mail Kirk Conger at kconger2@unl.edu.
About this series
This story is one in a series spotlighting campuswide efforts to conserve energy and save money.
Do your part to help UNL save money by cutting energy costs. See www.unl.edu/unlpub/special/energy/ to learn other money-saving ideas.
GO TO: ISSUE OF FEBRUARY 12
NEWS HEADLINES FOR FEBRUARY 12
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Fans keep Hamilton Hall safe, efficient
Museums to present ‘Dinosaur Detectives’
‘Simpsons’ producer to speak Feb. 18 at Union
Team earns trophy for SAFER wall
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